1. Field of the Invention
The present invention relates to an integrated circuit device, and particularly relates to an integrated circuit device having a multi-layer wiring structure made of Al or an Al alloy.
2. Description of the Related Art
In a conventional integrated circuit device such as an LSI, a two-layer wiring structure as shown in FIG. 4 has been adopted.
In FIG. 4, a first wiring layer 14 consisting of Al or an Al alloy is formed over the surface of a semiconductor substrate 10 of silicon or the like on an underlying insulating film 12 of silicon oxide or the like. On the insulating film 12, an interlayer insulating film 16 of PSG (phospho-silicate glass) or the like is formed on the upper surface of the insulating film 12 so as to overlie the wiring layer 14. A connecting hole 16A corresponding to a portion of the wiring layer 14 is formed in the insulating film 16. A second wiring layer 18 of Al or an Al alloy is formed on the upper surface of the insulating film 16 so as to be connected to the wiring layer 14 through the connection hole 16A. In FIG. 4, the symbol G represents a grain, the symbol GB represents a grain boundary, and the line S--S' represents the interface between the first and second wiring layers 14 and 18.
According to the above-mentioned conventional wiring structure, there has been a ease where voids occur in the interface between the wiring layers 14 and 18, which corresponds to the line S--S'.
Further, it is known that Al atoms are made to electromigrate by electrons if a current, of which current density is beyond 10.sup.5 A/cm.sup.2, is supplied to an Al wire.